diff --git a/helusers/models.py b/helusers/models.py
index a7121d4..eb9d693 100644
--- a/helusers/models.py
+++ b/helusers/models.py
@@ -1,5 +1,7 @@
 import logging
 import uuid
+from collections import defaultdict
+from itertools import chain
 
 from django.contrib.auth.models import AbstractUser as DjangoAbstractUser
 from django.contrib.auth.models import Group
@@ -87,16 +89,18 @@ def sync_groups_from_ad(self):
         """Determine which Django groups to add or remove based on AD groups."""
 
         ad_list = ADGroupMapping.objects.values_list("ad_group", "group")
-        mappings = {ad_group: group for ad_group, group in ad_list}
+        mappings = defaultdict(list)
+        for ad_group, group in ad_list:
+            mappings[ad_group].append(group)
 
         user_ad_groups = set(
             self.ad_groups.filter(groups__isnull=False).values_list(flat=True)
         )
-        all_mapped_groups = set(mappings.values())
+        all_mapped_groups = set(chain(*mappings.values()))
         old_groups = set(
             self.groups.filter(id__in=all_mapped_groups).values_list(flat=True)
         )
-        new_groups = set([mappings[x] for x in user_ad_groups])
+        new_groups = set(chain(*[mappings[x] for x in user_ad_groups]))
 
         groups_to_delete = old_groups - new_groups
         if groups_to_delete:
diff --git a/helusers/tests/test_models.py b/helusers/tests/test_models.py
index 9c8829e..26c8954 100644
--- a/helusers/tests/test_models.py
+++ b/helusers/tests/test_models.py
@@ -160,6 +160,32 @@ class TestUserAdGroups:
                 [],
                 id="all_removed",
             ),
+            # many ad-group for 1 user group
+            pytest.param(
+                (
+                    ("ad_group_1", "group_1"),
+                    ("ad_group_2", "group_1"),
+                    ("ad_group_3", "group_1"),
+                ),
+                [],
+                [],
+                ["ad_group_1", "ad_group_2", "ad_group_3"],
+                ["group_1"],
+                id="one-ad-for-many-group",
+            ),
+            # 1 ad-group for many user groups
+            pytest.param(
+                (
+                    ("ad_group_1", "group_1"),
+                    ("ad_group_1", "group_2"),
+                    ("ad_group_1", "group_3"),
+                ),
+                [],
+                [],
+                ["ad_group_1"],
+                ["group_1", "group_2", "group_3"],
+                id="many-ad-for-one-group",
+            ),
         ],
     )
     def test_update_ad_groups(